Both sites commemorate the efforts of Guglielmo Marconi to transmit transatlantic radio signals between North America and Europe in the first decade of the 20th century.

Signal Hill in St. John's, Newfoundland and Labrador is another National Historic Site related to Marconi's work in Canada.

A spark gap transmitter with 75 kilowatts of power fed four tall antennas on the 2-hectare (4.9-acre) site overlooking the ocean.

In December 1902 Marconi transmitted the first complete messages to Poldhu from stations at Glace Bay, Nova Scotia.

Communications between Glace Bay and England proved to be unreliable, and only possible after dark, so Marconi had larger stations constructed on both sides of the Atlantic between 1905 and 1907.